At present, the binocular telescope with laser ranging function has the problem that it cannot meet the requirements of actual mass production from the point view of optical mechanical properties. The products with good performance have complex optical mechanical structure and difficult process, while the low-end products cannot meet the actual application requirements due to poor performance The erecting prism used by the binocular telescope with laser ranging function includes Porro prism, Schmidt-Pechan prism and Abbe prism. By comparison, it is found that the Porro prism has slightly smaller qualified field of view and large space volume when the same material is used, so the final product is relatively bulky. The Schmidt-Pechan prism is compact in size but has high light loss, and it is difficult to enlarge the aperture. The structure is too complex after the beam splitter prism required for laser ranging is compounded, and changes in the shape such as back bulging caused by the required space result in an unsightly product. The size of the Abbe prism is between the above two, and its optical property is superior to the above two. Such prism has large qualified field of view and low light loss. However, its complex production process may result in high price.
Therefore, it is necessary to improve the prior art.
As shown in FIG. 1, the existing erecting prism group for binocular telescope with laser ranging function, Patent No. ZL201020133893.4, an erecting prism group capable of displaying optical virtual sight and character information, showing a simple coincidence system. Such prism group usually composed of a roof prism and an isosceles prism can reverse the image formed by the front system (such as the objective lens) and transfer it to the rear system (such as the ocular) in the light path.
Although the system can display the additional graphics and text information based on imaging principle of lens and beam splitter principle of prism plane, it still has two obvious insurmountable defects. One is that the space provided by the prism to the display device is narrow, resulting in a small field of view, only one third of the field of view of the other light path. For example, only a line of simple four-digit characters can be displayed, and a large field of view for display of graphics and text information cannot be achieved. The other is that the beam splitting film is far from the normal incidence, resulting in a system transmittance of less than 35%, and the brightness of the displayed image is extremely low and the product cannot be used in the daytime. Therefore, it is difficult to see the characters due to narrow space, simple structure, poor imaging quality, and unclear additional graphics and text information of the imaging lens group.